Advances in manufacturing techniques have allowed transistors to be made with smaller geometries. For example, photolithographic and etch techniques have improved to the point where transistors with a gate length of less than 0.10 microns (μm) may be made. Decreasing the size of transistors is generally perceived to be beneficial because this may allow more transistors to be made within the same amount of area on a semiconductor die.
However, as the gate length of a transistor is reduced, the distance between the current carrying electrodes (e.g., source and drain terminals) may also be proportionately reduced. Consequently, the amount of semiconductor material between these terminals and beneath the gate of the transistor, often referred to as a channel or body region, may be reduced. As the length of the channel region of a transistor is reduced, the electric field of the drain terminal may have a greater effect upon the flow of current in the channel region. Thus, reductions in channel length may make it more difficult to control the flow of current across the channel region between the source and drain terminals and lead to an increase in the amount of source-to-drain leakage (e.g., off-state current).
Techniques to address this leakage current may involve applying a voltage potential to the bulk or channel region when the transistors are inactive. However, such techniques often involve the use of additional metal lines that are routed across an integrated circuit to provide the leakage reducing voltage potential. This, in turn, may increase the complexity and cost of the manufacturing process. Thus, there is a continuing need to reduce the leakage current between the current carrying electrodes of transistors.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.